Cross-hole Electromagnetic Inversion and Applications

Abstract

In this study, practical method for inverting cross-hole EM data to reconstruct a resistivity distribution is presented. The prior information constraint is incorporated into an iterative, regularized inversion method, with a variable roughness added into the inversion process. A forward solver that is based on the two and half dimensional (2.5D) model has been developed by using the finite element method (FEM) to evaluate both the forward problem and the “pseudo-forward” problem needed to construct the sensitivity matrix. In our field data, a vertically oriented magnetic dipole has been employed as a transmitter and multi-component receiver system has been applied to acquire the magnetic field data. The regularized least-squares inversion scheme, which is constrained with the a priori information obtained from well logging, is adopted to reconstruct the inter-well resistivity profile from the synthetic electromagnetic data and the field data acquired in oil field. The synthetic and field data examples indicate that our method is robust and stable in the presence of random noise.